Spraying apparatus and control system therefor

ABSTRACT

A spraying device comprising a spray boom, a plurality of nozzles attached to the spray boom and a pressure responsive valve for each of the nozzles. Each of the valves has an open position and a closed position for, respectively, permitting and preventing the flow of sprayable fluid through the associated nozzle. The valves are actuated hydraulically and when opened, sprayable fluid is supplied through the boom and the valves to the nozzles.

United States Patent [151 3,

Barlow Aug. 15, 1972 SPRAYING APPARATUS AND 2,579,792 12/1951 Cartwright..239/551 CONTROL SYSTEM THEREFOR 3,392,919 7/1968 Wies ..239/455Inventor: Conrad R. Barlow, Redondo Beach,

Calif.

Assignee: Transland Aircraft, lnc., Harbor City, Calif.

Field of Search ..239/551, 571, 124, 537, 569, 239/570, 534, 546, 455,171

References Cited UNITED STATES PATENTS 1 H1966 Broughton ..239/602Primary Examiner-Lloyd L. King AtlorneySmyth, Roston & Pavitt 5 7ABSTRACT A spraying device comprising a spray boom, 21 plurality ofnozzles attached to the spray boom and a pressure responsive valve foreach of the nozzles. Each of the valves has an open position and aclosed position for, respectively. permitting and preventing the flow ofsprayable fluid through the associated nozzle. The

valves are actuated hydraulically and when opened. sprayable fluid issupplied through the boom and the valves to the nozzles.

12 Claims, 5 Drawing Figures PAIENTEnAus 15 I972 3.684 177 SHEET 1 0F 2[imam 5 SPRAYING APPARATUS AND CONTROL SYSTEM THEREFOR BACKGROUND OF THEINVENTION It is often necessary to spray various liquids such asinsecticides, fungicides, etc. for agricultural purposes. This can berapidly carried out by a spraying apparatus which is associated with avehicle such as an airplane. In one such system, a spray boom isattached to a fixed wing airplane along the wing thereof, and thesprayable liquid is supplied to the boom. A plurality of nozzles areaffixed to the boom to receive and spray the sprayable liquid. A maincontrol valve controls the supply of sprayable fluid under pressure tothe boom. A secondary valve is associated with each of the nozzles, andeach of the secondary valves typically includes a diaphragm which isspring biased against a valve seat. The secondary valves are opened bythe pressure of the sprayable fluid supplied through the spray boom whenthe main control valve is open.

One disadvantage of this system is that particulate matter may betrapped between the valve seat and the diaphragm. When this occurs, thevalve lealt'sbecause the spring has insufficient force to completelyclose the valve when the particulate matter is trapped therein.

The spring cannot be made stronger without increasing the pressure atwhich the sprayable liquid must be provided to open the valve. Leakagenot only results in wasting of the sprayable fluid but also may causedamage if the sprayable fluid is a dangerous insecticide or fungicide orother chemical which may be incompatible with the object upon which itfalls.

Another problem with this prior art system is that the spring may weakenthrough use, or due to manufacturing tolerances may not providesufficient force on the diaphragm. When this occurs, the sprayable fluidwhich may, under certain circumstances, be under a small static headopens the secondary valve slightly and causes leakage.

SUMMARY OF THE INVENTION The present invention solves the problems notedabove by providing a secondary valve for a spraying system which isactuated by an actuating fluid under pressure such as a suitablehydraulic fluid. In one form of the present invention, the hydraulicfluid is usedto close the secondary valve. This results in very tightclosure of the valve and positively prevents leakage. Opening of thesecondary valve is facilitated because the actuating fluid can bedepressurized whenever it is desired to open the secondary valve. Withthe actuating fluid under substantially no pressure, the sprayablefluid, even at relatively low pressures thereof, can open the secondaryvalve, and it is not necessary to overcome any spring force.

In another form of the present invention, the actuating fluid is used toopen the secondary valve. With this form of the invention, a relativelyheavy spring normally maintains the valve in a closed position. Thespring provides a much greater force than could reasonably be toleratedif the valve were to be open by the pressure of the sprayable fluid.This form of the invention has the advantage of failing safe in theevent of a loss of hydraulic pressure. The pressure of the actuatingfluid is sufficient to overcome the relatively heavy spring and open thevalve so that the sprayable fluid need not perform the valve openingfunction. Of course, if desired, the pressure of the actuating fluid andthe pressure of the sprayable fluid could be used simultaneously to openthe valve.

For both forms of the invention, actuating fluid under pressure can beadvantageously supplied by a master cylinder of the type typically usedin an automobile braking system. Upon command of the operator, themaster cylinder is operated to selectively pressurize or depressurizethe actuating fluid to thereby control the action of the secondaryvalves. With this arrangement operation of the secondary valve is notdependent upon the aircraft hydraulic system.

The present invention employs a main control valve for controlling theflow of sprayable fluid to the spray boom. This main control valve canadvantageously take the form of a three-way valve having an inletconnected to the supply tank of sprayable fluid and two outletsconnected, respectively, to the spray boom and to the spray tank. Thethree-way valve receives sprayable fluid under pressure from a pump andeither returns it to the supply tank or supplies it to the spray boom orproportions the flow therebetween. v

Another feature of the present invention is the use of a common controlmember to simultaneously operate the main control valve and the mastercylinder. With this arrangement, movement of the control member by theoperator results in substantially simultaneously opening the maincontrol valve and the secondary valves, or in closing the main controlvalve and the secondary valves. An over-center mechanism is used toadvantage to maintain the master cylinder in the position in which itsupplies fluid under pressure to the secondary valves.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view of aspraying system constructed in accordance with the teachings of thisinvention.

FIG. 2 is a sectional view through the spray boom at one of thesecondary valves showing one form of secondary valve constructed inaccordance with the teachings of this invention with the valve beingheld in the closed position by hydraulic fluid under pressure.

FIG. 2a is a sectional view similar to FIG. 2 with the valve being inthe open position.

FIG. 3 is a sectional view similar to FIG. 2 showing a second form ofsecondary valve with the valve being held in the closed position by arelatively stiff spring.

FIG. 3a is a sectional view similar to FIG. 3 with the secondary valvebeing held in the open position by hydraulic fluid under pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing and inparticular to FIG. 1 thereof, reference numeral 11 designates a sprayingsystem constructed in accordance with the teachings of this invention.The system 11 is carried by a vehicle such as a fixed wing aircraft (notshown). The system 15 from the tank 13 through a conduit 19 to athreeway, main control valve 21.

The main valve 21 directs the sprayable fluid supplied thereto by thepump 17 to, either or both of, the

conduits 23 and 25. The sprayable fluid supplied to the conduit 23 isreturned to the tank 13 and preferably to the lower regions thereof tomaintain the sprayable fluid 15 properly mixed. The sprayable fluid ldirected to the conduit 25 is supplied to a spray boom 27 which in turndistributes the sprayable fluid to a plurality of spray assemblies 29,any number of which may be utilized. As shown in the illustratedembodiment the spray assemblies 29 are arranged in parallel. The sprayboom 27 may be attached to the wing of the airplane with the sprayassemblies 29 appropriately arranged to spray the sprayable materialaway from the boom.

The spray assemblies 29 can be maintained in an open or closed positionby a master cylinder 31 which pressurizes or depressurizes hydraulicfluid in a conduit 33 leading from the master cylinder to each of theassemblies 29. The master cylinder 31 can be of any design which willpressurize hydraulic fluid in response to a predetermined input motionand as such may be of the type used in automobile braking systems. Suchinput motion is supplied by a control member 35 which is suitablypivotally mounted intermediate its ends to a fixed support member 37.The pivotal movement of the control member 35 is transformed into linearinput motion to an input member 39 of the master cylinder by a pair oflinks 41 and 43. As shown in FIG. 1, the link 41 is pivotally connectedto the link 43 and to a rigid link 45 which forms a part of the controlmember 35. The link 43 is pivotally connected to another portion of thefixed support 37. The linkage between the control member 35 and theinput member 39 can be slotted as necessary to provide the desired inputmotion to the input member.

The control member 35 also operates the main valve 21. This isaccomplished by a link 46 interconnecting the lower end of the controlmember 35 and an operating handle 47 of the main valve.

The control member 35 is pivotal about an axis between the full lineposition and the dotted line position shown in FIG. 1. In the full lineposition, the master cylinder does not pressurize the hydraulic fluid,and according to the first embodiment of the invention, the sprayassemblies 29 are open in this condition. The main valve 21 is also openso that the main valve 21 supplies all of the sprayable fluid 15supplied thereto by the pump 17 to the spray boom 27 via the conduit 25.Accordingly, in this position of the control member 35, the sprayablefluid is discharged from the assemblies 29. In this position of thecontrol member 35, there are substantially no forces tending to move thecontrol member toward the dotted line position, and accordingly, no stopor latching mechanism is necessary to retain the control member in thisposition; however, a stop may be provided, if desired.

In the dashed line position shown in FIG. 1, the input member 39is movedaxially to the right relative to the remainder of the master cylinder 31thereby causing the latter to pressurize, in a conventional manner, thehydraulic fluid which is supplied to the spray assemblies 29. Accordingto the first embodiment of this invention, this results in closing ofthe spray assemblies 29. In addition, the operating handle 47 is movedso that all of the sprayable fluid 15 supplied thereto by the pump 17 isreturned via the conduit 23 to the supply tank 13.

In the dashed line position, the reaction force resulting frompressurization of the hydraulic fluid by the master cylinder 31 tends tomove the input member 39 to the left as viewed in FIG. 1. It should benoted, however, that the links 41 and 45 are over-center in thisposition. Moreover, the main valve 21 has a stop 49 which preventsfurther over-center movement of the links 41 and 45. Accordingly, onceplaced in the off or dashed line position, the control member 35 remainsthere until moved by the operator.

The main valve 21 can also proportion the flow of sprayable fluidbetween the conduits 23 and 25. Accordingly, the control member 35 maybe maintained in a position intermediate the dashed and full linepositions shown in FIG. 1 by the operator or a suitable adjustable stop(not shown) can be provided to retain the control member 35 in theselected position. The control linkage is arranged so that the pressureof the hydraulic fluid is reduced by the master cylinder 31 to allowopening of the assemblies 29 at the position of the control member 35 atwhich the main control valve 21 supplies minor quantities of thesprayable fluid to the assemblies 29. Further movement of the controlmember 35 toward the open or full line position results in increasingthe flow rate of sprayable fluid through the spray boom 27.

A venturi 51 is located in the conduit 23 and a conduit 53 interconnectsthe conduit 25 with the constricted region of the venturi. With the mainvalve 21 turned off, the low static pressure at the constricted regionof the venturi 51 applies suction to the conduit 25 tending to pull theliquid therein into the conduit 23.

FIGS. 2 and 2a show the details of a typical one of the assemblies 29affixed to the boom 27. The spray boom 27 in the embodiment illustratedis a substantially cylindrical pipe having a passage 58 extendingtherethrough and one bushing 59 suitably mounted thereon as by weldingfor each of the assemblies 29. The assemblies 29 are identical, andaccordingly, only one of the assemblies 29 is illustrated in detail. Theassembly 29 has an inlet section 61 received within and attached to thebushing 59 with screw threads.

The assembly 29 generally includes a secondary valve 62 and a nozzle 64.The assembly 29 includes body sections 63 and 65 having passages 67 and69, respectively. The body sections 63 and 65 are held together incoaxial relationship by a retainer 71 which engages an annular shoulderon the body section 63 and which is affixed to the body section 65 byscrew threads. A flexible, resilient diaphragm 73 is clamped between theconfronting end faces of the body sections 63 and 65.

The body section 65 has a sleeve 75 therein which terminates in anannular valve seat 77. An annular passage 79 surrounds the sleeve 75.The passage 69 terminates in one or more orifices 81 formed in thenozzle 64.

A plunger 83 having an enlarged head 85 and a pressure responsive face87 is mounted for sliding movement in the passage 67. Hydraulic fluidunder pressure is supplied through a fitting 89 to the pressureresponsive face 87. The fitting 89 is mounted on the body section 63 byscrew threads 91 and a nut 93 with the interface between the fitting andthe body section 63 being sealed by an annular seal 95 such as anO-ring. Another annular seal 97 which may also be an O-ring is mountedin an annular groove in the body section 63 and isolates the pressureresponsive face 87 from a chamber 99 in which the head 85 is positioned.The chamber 99 is vented to atmosphere by a port 101 which extendsthrough the wall of the body section 63.

With the spraying system 11 attached to an aircraft, the operation ofthe spraying system can be controlled by the pilot by manually movingthe control member 35. With the control member 35 in the off or dashedline position shown in FIG. 1, hydraulic fluid under pressure from themaster cylinder 31 acts on the pressure responsive face 87 and urges theplunger 83 to the position shown in FIG. 2. In this position, the head85 of the plunger 83 urges the resilient diaphragm 73 into substantiallyfluid-tight sealing contact with the valve seat 77. Accordingly, anysprayable fluid in the passage 58 of the spray boom 27 cannot flowthrough the valve 62 to the orifice 81.

With the control member 35 in the off position, the main control valve21 blocks flow of the sprayable fluid through the conduit 25 to thespray boom 27. Accordingly, the fluid supplied by the pump 17 isreturned to the tank 13 via the conduit 23. The flow of the sprayablefluid 15 through the venturi 51 produces a region of low static pressureat the constricted region of the venturi to cause the sprayable fluidtrapped in the con-' duit 25 and the spray boom 27 to be drawn or suckedinto the conduit 23 and returned to the tank 13. Notwithstanding the useof the venturi 51, some of the sprayable fluid may remain in the sprayboom 27. Moreover, if the pump 17 is shut down as when the aircraft ison the ground, the flow, if any, through the ven turi 51 is notsufricient to create or to maintain a low static pressure region in theventuri. Accordingly, the sprayable fluid l5 flows from the tank 13through the conduits 23, 53 and 25 to the spray boom 27. Under thesecircumstances the sprayable fluid in the spray boom 27 is undera statichead depending upon the height of the fluid 15 in the tank 13 above thespray boom. Under these conditions, it is very important that theplunger 83 cause the diaphragm 73 to form-a tight seal against the valveseat 77. The hydraulic system of this invention provides such a tightseal and the seal thus provided is not dependent upon operation of theaircraft hydraulic system.

When the pilot wishes to spray the fluid 15, he merely moves the controlmember 35 to the on or full line position shown in FIG. 1. Thissimultaneously causes the master cylinder 31 to depressurize thehydraulic fluid acting against thepressure responsive faces 87 and movesthe three-way valve so that it supplies the sprayable fluid 15 to thespray boom 27. The pressure drop at the pressure responsive face 87allows the sprayable fluid 15 in the boom 27 and/or the resilience ofthe diaphragm 73 to easily move the diaphragm 73 and the plunger 83 tothe left as shown in FIG. 2a thereby opening the valve and permittingflow to the nozzle 81. The control member 35 need only be moved towardthe off position sufficiently to depressurize the hydraulic fluid sothat the pressure of the sprayable fluid can open the plunger 83. Oncethe diaphragm 73 separates from the valve seat 77, the pressure of thesprayable fluid acts over the whole area thereof. By moving the controlmember 35 further toward the on position, the valve 21 is caused tosupply greater portions of the sprayable fluid 15 to the spray boom 27.The diaphragm 73 is closely adjacent the valve seat 77 in the openposition of the valve 62. The diaphragm lies intermediate the plunger 83and the valve seat.

FIGS. 3 and 3a show a second embodiment of spray assembly 290 which isquite similar to the spray assembly 29 except that the former ismaintained in a closed position by a relatively heavy spring and isopened by hydraulic fluid under pressure. Portions of the spray assembly29a corresponding to portions of the spray assembly 29 are designated bycorresponding reference numerals followed by the letter a.

In FIG. 3, the plunger 83a includes a head 85a and a piston 121interconnected by a rod .123. One side of the piston 121 defines apressure responsive face 870 with the pressure responsive face 87a beingsealed from the head 85a and the chamber 99a by an O-ring seal 97a. Theplunger 83a and the body section 63a define an annular chamber to whichhydraulic fluid is supplied by a pair of fittings 127 and 129 which areconnected to the master cylinder 31 substantially as shown in FIG. 1.

The secondary valve 620 is normally urged to the closed position by arelatively heavy coil spring 131 which acts between the piston 121 andan end wall 133 of the body section 63a. This portion of the bodysection 63a is sealed from the chamber 125 by an annular seal 135.

In operation of the assembly 29a, the spring 131 normally forces theplunger 83a to the right to urge the diaphragm 73a into substantiallyfluid-tight sealing engagement with the valve seat 77a. When theoperator wishes to open the valve, he supplies hydraulic fluid underpressure through the fittings 127 and 129 to the chamber 125. Thehydraulic fluid under pressure acts on the pressure responsive face 87ato move the plunger 83a to the left to the position shown in FIG. 3a.This allows the diaphragm 73a to separate from the valve seat 770 tothereby open the passage to the orifice 81a. In all other respects thespray assembly 29a may be identical to the spray assembly 29.

If desired, the assemblies 29a can be utilized in the control systemshown in FIG. 1 in lieu of the spray assemblies 29. If this is done, theoperation of the control system will be the opposite of that describedhereinabove in that the dashed line position which results inpressurization of the hydraulic fluid will be the open position (FIG.3a). This means that the valve 21 must be reversed so that it willsupply the sprayable fluid 15 to the spray boom when the control member35 is in the dashed line position.

Although illustrative embodiments of the invention has been shown anddescribed, many changes, modifications, and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

lclaim:

l. A spraying system for spraying a sprayable fluid and operable by anactuating fluid, said spraying system being attachable to an aircraftand comprising:

a spray boom having a passage therein through which the sprayable fluidcan flow;

nozzle means attached to the spray boom for receiving sprayable fluidtherefrom and for spraying such sprayable fluid; pressure responsivevalve means having an open position and a closed position for,respectively, permitting and preventing the flow of sprayable fluidthrough said nozzle means; I

first means for supplying actuating fluid under pressure to the valvemeans to place the valve means in one of said positions thereof;

second means for supplying the sprayable fluid under pressure to thespray boom at least when said valve means is in said open position; and

said valve means including a valve body having a passageway therein, avalve seat in said body, a diaphragm mounted in said body adjacent saidvalve seat for movement toward and away from said valve seat, a plungermounted in the passageway of said valve body with the diaphragm beingintermediate said plunger and said valve seat, the actuating fluid underpressure being directed to the plunger to cause movement thereof,movement of the plunger toward the valve seat urging the diaphragm intosubstantially fluid tight sealing engagement therewith whereby saidvalve means is in said closed position thereof.

2. A spraying system as defined in claim 1 including a control memberand means for mounting said control member for movement between firstand second positions, said first means being responsive to the controlmember being in said first position thereof for supplying actuatingfluid under pressure to the valve means to place the valve means in saidone position thereof, said spraying system including third meansresponsive to the surizing the actuating fluid to place the valve meansin said one position thereof, said master cylinder also being capable ofreducing the pressure of the actuating fluid to thereby permit the valveto be placed in the other position thereof.

4. A spraying system as defined in claim 1 wherein said one position ofsaid valve means is said closed position and said first means suppliesactuating fluid under pressure to the plunger to force the latter towardsaid valve seat.

5. A spraying system as defined in claim 1 wherein said one position ofsaid valve means is said open position, said plunger having a facesubstantially isolated from said diaphragm, and said first meanssupplies actuating fluid under pressure to said face of said plunger tomove said plunger away from said valve seat to thereby place said valvemeans in said open position, said spraying system including resilientmeans for urging the plunger toward the valve seat.

6. A control system for a spraying device of the type which isattachable to an aircraft and sprays a sprayable fluid through a nozzle,said control system comprising:

a valve assembly attached to said nozzle;

said assembly including a body having a passage therein and means forconnecting said body to the spraying device, said body having an inletfor receiving the sprayable fluid from the spraying device, said nozzlereceiving the sprayable fluid from said passage;

a valve seat in said passage of said body;

a diaphragm in said passage of said body movable toward and away fromthe valve seat and engageable therewith to form a substantially fluidtight seal in said passage of said body downstream from said inlet tothereby shut-off the flow of sprayable fluid to the nozzle;

a plunger mounted in said passage of said body for movement between afirst position in which said plunger urges said diaphragm intosubstantially fluid-tight sealing engagement with said valve seat and asecond position in which said plunger does not urge said diaphragm intosubstantially fluidtight sealing engagement with said valve seat, saiddiaphragm being intermediate said plunger and said valve seat, saidplunger having a fluid pressure responsive face thereon; and

means for supplying actuating fluid under pressure to the fluid pressureresponsive face of said plunger to thereby urge said plunger to one ofsaid positions thereof.

7. A control system as defined in claim 6 wherein the supply ofactuating fluid under pressure to said pressure responsive face urgessaid plunger toward said valve seat to shut-ofl the supply of sprayablefluid to the nozzle.

8. A control system as defined in claim 6 including a relatively heavyspring for normally urging said plunger toward said valve seat tothereby maintain the supply of sprayable fluid to the orifice shut-off,the supply of actuating fluid under pressure to said pressure responsiveface of said plunger urging said plunger away from said valve seat tothereby permit the sprayable fluid to flow through the passage of thebody to the nozzle.

9. A control system for a spraying device of the type which isattachable to an aircraft and sprays a sprayable fluid through nozzlemeans, said control system comprising:

pressure responsive valve means having an open position and a closedposition for, respectively, permitting and preventing the flow ofsprayable fluid through said nozzle means;

a control member;

means for mounting the control member for movement between first andsecondpositions;

first means responsive to the control member being in said firstposition thereof for supplying an actuating fluid under pressure to thepressure responsive valve means to place the pressure responsive valvemeans in one of said positions thereof;

second means responsive to the control member being in said secondposition thereof for permitting the valve means to be in the otherposition thereof;

third means responsive to the control member being in the positionthereof corresponding to the open position of said pressureresponsive-valve means for supplying sprayable fluid under pressure tothe pressure responsive valve means; and

said first means including a master cylinder for pressurizing theactuating fluid and said third means including valve means forcontrolling the flow of sprayable fluid under pressure to the nozzle andthe pressure responsive valves can be opened and closed. 11. A sprayingsystem as defined in claim 10 wherein said first means includes a mastercylinder, said commeans, said control system also including linkage moncontrol means includes overcenter toggle means means for i t rc ti id tl member for holding the master cylinder in the position in which I withsaid last mentioned valve means and said It Provides actuating fluiqlunder Pressure 9 the P master cylinder, said linkage means includingover sure responslve Valvesv 69mm] Valve belllg at least center togglemeans for retaining said control a three-way valve for receiv ngsprayable fluid from a member in one of Said positions thereof con 10source and directing the flu d to the pressure responresponding to theposition in which the master valves or biick toward source' cylinderpressurizes the actuating fluid. A Spraymg System for sprayable fl ff;531d 10. A spraying system for a sprayable fluid, said Zil j bbemg aspray ng System being attachable to an aircraft and 15 y gazg gg s glactuatmg Sal p y gi a zg g gz an actuatmg fluld sald Spraymg nozzlemeans for discharging the sprayable fluid;

a plurality of nozzles arranged in parallel for presslP-F responsivevalve F havmg an .open discharging the sprayable fluid position and aclosed position for, respectively,

conduit means for su l in the sprayable fluid to pemmng and-prevemmg theflow of sprayable the nozzles pp y g fluid through said nozzle means;

a plurality of pressure responsive valves for said noza master cylmdeifor Supplymg actuE-mg fluld under- I d H l d pressure to said pressureresponsive valve means 2 2 22255 ig g i i lg ggggg gss to plzi ce sjaidpressure1 I'GSPfOIISlVC valve means in oneo sai posltlonst ereo glllfrgl l t gg az s oggigd igzgl g fit gozgg conduit means for supplyingsprayable fluid to the y nozzemeans; firililili i?S11;1355221;iiiiiifllll dillfiii ti e 0w 0 e spraya e m t oug sal con u1t sure to saidpressure responsive valves to place means to the pressure responsivevalve means; Said Pressure responsive Valves in one Ofsaid P commoncontrol means for operating said master lions thereof; c linder and saidco trol valve; d

a control valve for selectively allowing and blocking 5318, Commoncontrol means mafidmg overcfamer flow of the sprayable fluid throughsaid conduit 88 f a f holdmgthe "t cylmder the means to the pressureresponsive valves; and position in which it supplies fluid underpressure to common control means for operating said first means saldPressre responslve Valve meansand said control valve whereby the controlvalve

1. A spraying system for spraying a sprayable fluid and operable by anactuating fluid, said spraying system being attachable to an aircraftand comprising: a spray boom having a passage therein through which thesprayable fluid can flow; nozzle means attached to the spray boom forreceiving sprayable fluid therefrom and for spraying such sprayablefluid; pressure responsive valve means having an open position and aclosed position for, respectively, permitting and preventing the flow ofsprayable fluid through said nozzle means; first means for supplyingactuating fluid under pressure to the valve means to place the valvemeans in one of said positions thereof; second means for supplying thesprayable fluid under pressure to the spray boom at least when saidvalve means is in said open position; and said valve means including avalve body having a passageway therein, a valve seat in said body, adiaphragm mounted in said body adjacent said valve seat for movementtoward and away from said valve seat, a plunger mounted in thepassageway of said valve body with the diaphragm being intermediate saidplunger and said valve seat, the actuating fluid under pressure beingdirected to the plunger to cause movement thereof, movement of theplunger toward the valve seat urging the diaphragm into substantiallyfluid tight sealing engagement therewith whereby said valve means is insaid closed position thereof.
 2. A spraying system as defined in claim 1including a control member and means for mounting said control memberfor movement between first and second positions, said first means beingresponsive to the control member being in said first position thereoffor supplying actuating fluid under pressure to the valve means to placethe valve means in said one position thereof, said spraying systemincluding third means responsive to the control member being in saidsecond position thereof for permitting the valve means to be in theother position thereof, said second means being responsive to thecontrol member being in the position thereof corresponding to the openposition of said valve means for supplying sprayable fluid underpressure to the spray boom.
 3. A spraying system as defined in claim 1wherein said first means includes a master cylinder for pressurizing theactuating fluid to place the valve means in said one position thereof,said master cylinder also being capable of reducing the pressure of theactuating fluid to thereby permit the valve to be placed in the otherposition thereof.
 4. A spraying system as defined in claim 1 whereinsaid one position of said valve means is said closed position and saidfirst means supplies actuating fluid under pressure to the plunger toforce the latter toward said valve seat.
 5. A spraying system as definedin claim 1 wherein said one position of said valve means is said openposition, said plunger having a face substantially isolated from saiddiaphragm, and said first means supplies actuating fluid under pressureto said face of said plunger to move said plunger away from said valveseat to thereby place said valve means in said open position, saidspraying system including resilient means for urging the plunger towardthe valve seat.
 6. A control system for a spraying device of the typewhich is attachable to an aircraft and sprays a sprayable fluid througha nozzle, said control system comprising: a valve assembly attached tosaid nozzle; said assembly including a body having a passage therein andmeans for connecting said body to the spraying device, said body havingan inlet for receiving the sprayable fluid from the spraying device,said nozzle receiving the sprayable fluid from said passage; a valveseat in said passage of said body; a diaphragm in said passage of saidbody movable toward and away from the valve seat and engageabletherewith to form a substantially fluid tight seal in said passage ofsaid body downstream from said inlet to thereby shut-off the flow ofsprayable fluid to the nozzle; a plunger mounted in said passage of saidbody for movement between a first position in which said plunger urgessaid diaphragm into substantially fluid-tight sealing engagement withsaid valve seat and a second position in which said plunger does noturge said diaphragm into substantially fluid-tight sealing engagementwith said valve seat, said diaphragm being intermediate said plunger andsaid valve seat, said plunger having a fluid pressure responsive facethereon; and means for supplying actuating fluid under pressure to thefluid pressure responsive face of said plunger to thereby urge saidplunger to one of said positions thereof.
 7. A control system as definedin claim 6 wherein the supply of actuating fluid under pressure to saidpressure responsive face urges said plunger toward said valve seat toshut-off the supply of sprayable fluid to the nozzle.
 8. A controlsystem as defined in claim 6 including a relatively heavy spring fornormally urging said plunger toward said valve seat to thereby maintainthe supply of sprayable fluid to the orifice shut-off, the supply ofactuating fluid under pressure to said pressure responsive face of saidplunger urging said plunger away from said valve seat to thereby permitthe sprayable fluid to flow through the passage of the body to thenozzle.
 9. A control system for a spraying device of the type which isattachable to an aircraft and sprays a sprayable fluid through nozzlemeans, said control system comprising: pressure responsive valve meanshaving an open position and a closed position for, respectively,permitting and preventing the flow of sprayable fluid through saidnozzle means; a control member; means for mounting the control memberfor movement between first and second positions; first means responsiveto the control member being in said first position thereof for supplyingan actuating fluid under pressure to the pressure responsive valve meansto place the pressure responsive valve means in one of said positionsthereof; second means responsive to the control member being in saidsecond position thereof for permitting the valve means to be in theother position thereof; third means responsive to the control memberbeing in the position thereof corresponding to the open position of saidpressure responsive valve means for supplying sprayable fluid underpressure to the pressure responsive valve means; and said first meansincluding a master cylinder for pressurizing the actuating fluid andsaid third means including valve means for controlling the flow ofsprayable fluid under pressure to the nozzle means, said control systemalso including linkage means for interconnecting said control memberwith said last mentioned valve means and said master cylinder, saidlinkage means including over center toggle means for retaining saidcontrol member in one of said positions thereof corresponding to theposition in which the master cylinder pressurizes the actuating fluid.10. A spraying system for a sprayable fluid, said spraying system beiNgattachable to an aircraft and being operable by an actuating fluid, saidspraying system comprising: a plurality of nozzles arranged in parallelfor discharging the sprayable fluid; conduit means for supplying thesprayable fluid to the nozzles; a plurality of pressure responsivevalves for said nozzles arranged in parallel in said conduit means, eachof said valves having an open position in which sprayable fluid can passtherethrough and through the associated nozzle and a closed position inwhich flow of the sprayable fluid is blocked; first means for supplyingactuating fluid under pressure to said pressure responsive valves toplace said pressure responsive valves in one of said positions thereof;a control valve for selectively allowing and blocking flow of thesprayable fluid through said conduit means to the pressure responsivevalves; and common control means for operating said first means and saidcontrol valve whereby the control valve and the pressure responsivevalves can be opened and closed.
 11. A spraying system as defined inclaim 10 wherein said first means includes a master cylinder, saidcommon control means includes overcenter toggle means for holding themaster cylinder in the position in which it provides actuating fluidunder pressure to the pressure responsive valves, said control valvebeing at least a three-way valve for receiving sprayable fluid from asource and directing the fluid to the pressure responsive valves or backtoward said source.
 12. A spraying system for a sprayable fluid, saidspraying system being attachable to an aircraft and being operable by anactuating fluid, said spraying system comprising: nozzle means fordischarging the sprayable fluid; pressure responsive valve means havingan open position and a closed position for, respectively, permitting andpreventing the flow of sprayable fluid through said nozzle means; amaster cylinder for supplying actuating fluid under pressure to saidpressure responsive valve means to place said pressure responsive valvemeans in one of said positions thereof; conduit means for supplyingsprayable fluid to the nozzle means; a control valve for selectivelyallowing and blocking flow of the sprayable fluid through said conduitmeans to the pressure responsive valve means; common control means foroperating said master cylinder and said control valve; and said commoncontrol means including overcenter toggle means for holding the mastercylinder in the position in which it supplies fluid under pressure tosaid pressure responsive valve means.